This invention relates generally to an exit device for a door, and more particularly to a delayed egress exit device which may be used in a door security system.
Exit devices generally include a frame or housing secured across a door face and substantially spanning the width of the door. A touch bar is movably mounted to the frame. The touch bar is mechanically linked to a latch mechanism including a door latch which is movably mounted adjacent to a free edge of the door. Depressing the touch bar in the frame toward the door translates the mechanical linkage for actuating the latch mechanism in order to retract the door latch, which may be a rim latch or vertical rods with ceiling and floor latches, so that the door can be opened.
There are circumstances in which immediate opening of the door when the touch bar is pushed is not desirable, generally because some exit doors must remain secured until authorized personnel can arrive. For example, delayed egress exit devices are used on retail store doors to prevent shoplifters from escaping with stolen articles. If a shoplifter's exit can be delayed for a brief period of time, and a signal emitted when the exit device is pushed, store personnel will have an opportunity to monitor the exiting party. A delayed egress exit device is also useful for reasons of safety. For example, the security of a hospital or nursing home exit door should be maintained to delay persons from leaving without authority, or the proper assistance, in other than emergency situations. If a person's exit can be delayed long enough after the exit device is operated, they can be prevented from leaving.
Conventionally, delayed egress is accomplished through the combination of an exit device with an internal, electrically-powered delaying mechanism associated with the latch mechanism. The delaying mechanism is generally interposed between the touch bar and the door latch to prevent the immediate opening of the door. The delaying mechanism provides a delay period following an effort to exit through the door before actuating the door latch mechanism to retract the latch and allow the door to open. The preset delay period allows time for personnel to arrive at the site of the door, or otherwise respond if required to assist or prevent egress.
Delayed egress exit devices may further comprise audible or visual alarms at the location of the door, or at a remote location, to signify attempted egress or ingress. Such exit devices are often incorporated into overall security systems which readily interface with electromagnetic lock systems, including readers, touch pads, electronic keys or other personal identification security measures, to control both egress and ingress through the door.
Unfortunately, delayed egress exit device delay mechanisms generally require complicated internal arrangements to function properly. These complicated internal arrangements are difficult to manufacture and also may be prone to failure in critical emergency situations.
For the foregoing reasons, there is a need for a simple, reliable arrangement for use in an exit device for effecting delayed egress.